docker ps: always use --quiet, also combined with --format

[thaJeztah]

• follow-up to Fix psFormat's Size handling in config file #3640
• see the discussion on cli/command: ps: only check format-template once photra/cli#1 (comment)
• fixes docker ps -q does not work if the config file contains a psFormat  #4093
• supersedes / closes cli: do not apply configfile's psFormat when --quiet is passed #4040

Previously, the formatter would ignore the quiet option if a custom format
was passed; this situation was handled in runPs(), where custom formats
would only be applied if the quiet option was not set, but only if the
format was set in the CLI's config.

This patch updates NewContainerFormat() to do the same, even if a --format
was passed on the command-line.

This is a change in behavior, so may need some discussion; possible alternatives;

• produce an error if both --format and --quiet are passed
• print a warning if both are passed (but use the logic from this patch)

Before this patch:

docker ps --format '{{.Image}}'
ubuntu:22.04
alpine

docker ps --format '{{.Image}}' --quiet
ubuntu:22.04
alpine

mkdir -p ~/.docker/
echo '{"psFormat": "{{.Image}}" > ~/.docker/config.json

docker ps
ubuntu:22.04
alpine

docker ps --quiet
ubuntu:22.04
alpine

With this patch applied:

docker ps --format '{{.Image}}'
ubuntu:22.04
alpine

docker ps --format '{{.Image}}' --quiet
40111f61d5c5
482efdf39fac

mkdir -p ~/.docker/
echo '{"psFormat": "{{.Image}}" > ~/.docker/config.json

docker ps
ubuntu:22.04
alpine

docker ps --quiet
40111f61d5c5
482efdf39fac

docker ps: print warning if both --format and --quiet are set

Of both "--quiet" and "--format" are set, --quiet takes precedence. This
patch adds a warning to inform the user that their custom format is not
used:

docker ps --format='{{.Image}}'
ubuntu:22.04
alpine

docker ps --format='{{.Image}}' --quiet
WARNING: Ignoring custom format, because both --format and --quiet are set.
40111f61d5c5
482efdf39fac

The warning is printed on STDERR, so can be redirected:

docker ps --format='{{.Image}}' --quiet 2> /dev/null
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482efdf39fac

The warning is only shown if the format is set using the "--format" option.
No warning is shown if a custom format is set through the CLI configuration
file:

mkdir -p ~/.docker/
echo '{"psFormat": "{{.Image}}"}' > ~/.docker/config.json

docker ps
ubuntu:22.04
alpine

docker ps --quiet
40111f61d5c5
482efdf39fac

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

Merging #3666 (37e02ff) into master (d49b8ff) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3666   +/-   ##
=======================================
  Coverage   59.03%   59.04%           
=======================================
  Files         288      288           
  Lines       24776    24781    +5     
=======================================
+ Hits        14627    14632    +5     
  Misses       9265     9265           
  Partials      884      884           

[thaJeztah]

@vvoland @rumpl @laurazard PTAL (I added the warning we discussed during one of our triage sessions)

[thaJeztah]

Thx! Let me bring this one in 👍